The invention relates to a probe for dialysis with an ingoing and an outgoing line for the dialytic medium, comprising an insertion needle for introducing the probe, which needle is surrounded by a flexible plastic cannula, which in turn is surrounded, at least partly, by a tubular dialysing membrane connected to the plastic cannula at the distal end, forming a fluid-tight seal.
In German laid-open print DE-OS 33 42 170 a dialytic probe is disclosed which is used primarily for insertion in biological tissue and comprises a dialysing membrane as well as ingoing and outgoing lines for the dialytic medium. The probe is provided with a frame which supports the dialysing membrane but does not cover it entirely. The frame basically consists of a metal sleeve with an opening in its wall where the surface of the membrane is exposed and may be utilised for dialysis. The size and shape of this opening may vary according to the desired size and shape of the membrane surface available for dialysis, but will always be bounded by parts of the metal sleeve. The dialysing membrane is inserted into the frame with a tight fit against the wall of the frame, the distal ends of membrane and frame being glued together, for instance with the use of epoxide resin. The distal end of the probe is sealed by a semi-circular stopper bounding the interior of the probe. The ingoing and outgoing lines are configured as thin-walled metal tubes passing through a seal at the proximal end of the probe. The opening of one line is next to the distal end, whereas the opening of the other line is inside the probe next to the proximal end of the membrane.
Due to the frame being configured as a metal sleeve, the mechanical strength of the probe is good enough to permit insertion, which may considerably add to the patient's discomfort in certain long-term applications, however. Another disadvantage is that the parts of the probe's surface actually available for dialysis, are comparatively small.
A dialytic probe of the above type is described in U.S. Pat. No. 4,774,955, cf. FIGS. 4 and 5. This probe is provided with a hollow needle, which may be removed after the probe has been introduced, and which is surrounded by a plastic cannula. The plastic cannula in turn is surrounded by a tubular dialysing membrane bonded to the cannula at its distal and proximal end, forming a fluid-tight seal. Through a single feed line a fluid may be introduced into the space between plastic cannula and dialysing membrane, and is drained again through the same line for analysis. For this reason this type of probe will not permit continuous dialysis.
It is an object of the invention to propose a dialytic probe based on the known types of probes described above, which is easy to apply, comfortable to wear for prolonged periods of time, and which guarantees continuous circulation of the dialytic medium.